Method of sealing a metal tubulation



July 21, 1964 R. P. WATSON 3,141,225

METHOD OF SEALING A METAL TUBULATION Original Filed May 23, 1960 I uvmvron ROBERT P. WATSON TO EY HIS United States Patent 3,141,225 METHQD UF SEALING A METAL TUBULATION Robert P. Watson, Schenectady, N .Y., assignor to General Electric Company, a corporation of New York Original application May 23, 1960, Ser. No. 30,905.

Divided and this application Jan. 28, 1963, Ser. No.

Claims. (Cl. 29-251) My invention relates to electric discharge devices and pertains more particularly to new and improved methods of sealing a tubulation and processing an electric discharge device. This application is a division of my copending application Serial Number 30,905, filed May 23, 1960, and entitled Tubulation Seal and Method of Sealmg.

In the art of manufacturing electric discharge devices and similar other enveloped devices it is a common practice to aflix a metal tubulation to the envelope of the device for exhausting or gas charging purposes. Following exhaust or gas charging of the device throughthe tubulation the device including the tubulation is customarily sealed by pinching the end of the tube to effect a fusion or cold weld of the opposite sides of the tube. This manner of sealing the end of the tubulation results in a flared end which is invariably substantially wider than the normal outside diameter of the tubulation. Such a flare presents difficulty in fitting another member over or on the end of the tubulation. For example, in some electric discharge devices the tubulation is ordinarily sealed in an anode block and it is desirable to fit a heat radiator over the tubulation to effect dissipation of heat from the anode and to protect the tubulation from damage thus to avoid leakage. In such an arrangement it is also desirable that the radiator be rigidly fitted in place. When the tubulation end is flared by the pinch off step to a width greater than the normal outside diameter of the tubulation, it is difficult to fit a radiator thereover without providing an oversized bore to enable insertion therein of the flared tubulation end. Also, in such an arrangement it is not possible to fit the bored radiator tightly over the tubulation, and fastening means must be provided to hold the radiator tightly on the anode block. Additionally, and also by way of example, in some devices it is desirable to use the tubulation as an anode contact. When the tubulation end is flared in the above-discussed manner by a sealing pinch-off step it is diflicult, if not impossible, to fit an electrical connector over the end of the tubulation.

Another object of my invention is to provide a new and improved method of effecting the sealing of a tubulation.

Another object of my invention is to provide a new and improved method of processing an electric discharge device.

Another object of my invention is to provide a new and improved method of making an electrical contact arrangement for an electric discharge device.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In carrying out the objects of my invention I provide an electric discharge device including a reentrant anode block. The anode block includes an exhaust passage and fitted in the block to communicate with the passage is a metal exhaust tubulation. The diameter of the end portion of the tubulation is reduced and the extreme end is pinched with the width of the pinched portion no greater than the normal outer diameter of the tubulation. Tight ly fitted over the tubulation and engaging it over the length of the normal outer diameter portion thereof is a member having an inner diameter approximately the same as the normal outer diameter of the tubulation. This member can comprise either a heat radiator or an annular electrical connector. In manufacturing the device, a straight-walled tubulation is provided and fluid is drawn through the tubulation in the exhaust or gas charging of the device. Then the device is pinched off at a point outwardly spaced from the desired finished seal. Subsequently, the tubulation is reduced in diameter intermediate the pinch off and the device. Then a final pinch off is effected in the reduced-diameter region thus to provide the desired narrow-width flare.

For a better understanding of my invention reference may be had to the accompanying drawing in which:

FIG. 1 is an enlarged fragmentary sectional view of an electric discharge device incorporating an embodiment of my invention;

FIG. 2 is an enlarged fragmentary view illustrating a modified form of my invention; and

FIGS. 3-5 are enlarged fragmentary views illustrating the various steps in constructing a tubulation in accordance with a feature of my invention.

Referring to the drawing, there is shown in FIG. 1 an electric discharge device of the planar electrode type generally designated 1 and incorporating an embodiment of my invention. The device 1 includes an evacuated envelope 2 comprising a plurality of stacked annular ceramic and metal members comprising wall sections and annular contacts adapted for making electrical connections to a plurality of spaced cooperating electrode elements contained in the envelope and shown in outline.

One of the mentioned electrode elements is an anode 3 which can comprise a cylindrical metal block extending through the upper end wall of the envelope and including an active portion disposed in the envelope. The anode block 3 is provided with a central exhaust passage 4 which can communicate with the interior of the envelope by extending through the active inner end of the anode block, as shown, or alternatively, by communicating with a transverse passage opening on the lateral surfaces of the anode internally of the envelope.

The upper end of the anode 3 is counterbored and has tightly fitted and bonded therein an end of a metal exhaust tubulation 5. The tubulation 5 includes a protruding portion the end 6 of which is reduced in diameter relative to the normal outside diameter of the tubulation. At the reduced portion 6 is provided a pinched off seal or cold weld 7. The pinched off seal 7 constitutes a flared chisellike end. However, as seen in FIG. 1 the width of the pinched off end 7 is no greater than the normal outside diameter of the tubulation 5 and is preferably substantially less than the normal outside diameter of the tubulation.

Fitted over the tubulation 5 is a heat radiator 8 which can comprise a block of high heat conducting material. The radiator 8 includes a bottomed central bore 10 and a counterbore 11. The diameter of the bore 10 is such as to fit tightly over the portion of the tubulation 5, protruding from the end of the block and having the normal outside diameter, and the diameter of the counterbore 11 is such as to fit tightly over the outer end of the anode block. In this arrangement the narrow width of the pinch off or cold weld flare 7 presents no obstacle to the fitting of the radiator over the tubulation. Also, because the flared end 7 is narrower than the normal outer diameter of the tubulation, the bore 10 in the radiator need not be enlarged to fit over the flare and, thus, the inner diameter of the bore 10 can be desirably dimensioned for tightly fitting the tubulation which serves to rigidize the mounting of the radiator on the device.

Illustrated in FIG. 2 is a form of my invention applied to a device in which the tubulation 5 is utilized as an electrical contact. The tubulation of FIG. 2 can be identical in structure to that described above in regard to FIG. 1, and identical features bear identical numerals. However, instead of having a radiator fitted thereover, the tubulation of FIG. 2 is fitted with a contact cap or connector 12 which can be cup-like and have a lead 13 connected thereto. The cap 12 is sufiiciently deep such that when fitted on the end of the tubulation the side wall of the cap extends beyond the flared end 7 and engages the tubulation for a substantial distance over the normal outside diameter region. In this form of my invention the inside diameter of the cap 12 approximates the normal outside diameter of the tubulation such as to fit tightly on the tubulation. If the fiared end 7 were wider than the normal outside diameter of the tubulation, as found in the prior art, the fitting of a cap 12 upon the end of the tubulation in the manner shown in FIG. 2 would be impossible.

In manufacturing a device incorporating my invention one starts with an enveloped device of the type illustrated, for example, in FIG. 1 and including a uniformly straightwallcd metal tubulation. Then the device is processed, as for example, by evacuating or charging the envelope with gas through the tubulation. Following such processing, the tubulation is pinched off or cold welded at 15 which is at a point on the tubulation outward from the region at which it is desired to have a final pinch off 7 located. The pinch off 15 constitutes a first cold weld and, as seen in FIG. 3, is of the usual prior art type which is wider than the normal outside diameter of the tubulation. Such a pinch 01f would make impossible the fitting of a radiator or electrical connector cap of the types shown in FIGS. 1 and 2, respectively, over the end of the tubulation. Therefore, following the first pinch off 15 I reduce the diameter of the tubulation intermediate the pinch off 15 and the inner end of the tubulation by swaging, which can be effectively accomplished by passing the region of the tubulation to be reduced in diameter between a pair of oppositely rotating swaging dies 16 of predetermined width. This operation reduces the diameter of the tubulation in a manner shown in FIG. 4, and following such reduction of diameter a second pinch ofl? of the tubulation is effected in the region of reduced diameter in the manner shown in FIG. 5. Thus, a second cold weld is effected in the reduced region which is narrower than the normal outside diameter of the tubulation. The tubulation is cut at the dot and dash line 17, which is located outwardly of the cold weld 7, by the second pinch off step, leaving the narrow width tube pinch off 7 shown in FIGS. 1 and 2.

My just-described method of processing a tube, including the making of a final tubulation seal, is particularly attractive in sealing an electric discharge device following exhaust due to the fact that it allows the use of the full diameter of the tubulation for passage of fiuid during the exhaust while also providing a narrow width final pinch off. That is, during the exhaust step it is desirable that the tubulation not be necked down or reduced in diameter, since this would reduce the pumping or exhausting rate capacity of the tubulation. In my method the necking down of the tubulation to enable the formation of the narrow Width pinch olf takes place after the exhaust process is completed and thus makes available the large inside diameter of the tubulation throughout the whole length thereof for maximum pumping capacity.

Also, it is to be understood from the foregoing that while I have referred to the improved pinch off of my invention as being narrower in width than the normal outside diameter of the tubulation, in some devices the width of the pinch off need not be actually narrower but will be sufiicient if it is no greater than the normal outside diameter of the tubulation.

While I have shown and described specific embodiments of my invention, I do not desire my invention to be limited to the particular forms shown and described, and I intend by the appended claims to cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A method of sealing a metal exhaust tubulation of an electron discharge device, comprising the steps of reducing a portion of said tubulation to a diameter less than the normal outside diameter thereof and effecting a pinched off seal having a major width no greater than the normal outside diameter of said tubulation in said portion of reduced diameter.

2. A method of sealing a metal tubulation, comprising the steps of eifecting a first seal in said tubulation, then reducing a portion of said tubulation spaced from said seal to a diameter less than the normal outside diameter of said tubulation, and thereafter effecting a second seal with a major width no greater than said normal outside diameter of said tubulation in said portion of reduced diameter.

3. The method of exhausting an envelope, comprising evacuating said envelope through a metal tubulation sealed to said envelope and having a uniform straight inner wall, effecting a first pinched-off seal in said tubulation, reducing a portion of said tubulation between said first seal and said envelope to a diameter less than the normal outside diameter of said tubulation, effecting a second pinchedoff seal having a major width less than the normal outside diameter of said tubulation in said portion of reduced diameter, and removing the excess portion of said tubulation constituting the outer end portion from the second pinch off to the end having said first pinched-off seal.

4. In the method of making an electron discharge device having an apertured planar anode element supported in an envelope, the steps comprising, aifixing a straightwalled tubulation in said envelope and communicating with said anode element, exhausting said envelope through said tubulation, sealing the tubulation at a point outwardly spaced from a desired final seal point, reducing a transverse dimension of said tubulation in a region intermediate said outwardly spaced point and said final seal point, and effecting a seal in the reduced-diameter region.

5. The method of claim 4, further comprising the step of removing the portion of said tubulation beyond the last-mentioned seal.

References Cited in the file of this patent FOREIGN PATENTS 704,408 Great Britain Feb. 24, 1954 

1. A METHOD OF SEALING A METAL EXHAUST TUBULATION OF AN ELECTRON DISCHARGE DEVICE, COMPRISING THE STEPS OF REDUCING A PORTION OF SAID TUBULATION TO A DIAMETER LESS THAN THE NORMAL OUTSIDE DIAMETER THEREOF AND EFFECTING A PINCHED OFF SEAL HAVING A MAJOR WIDTH NO GREATER THAN THE NORMAL OUTSIDE DIAMETER OF SAID TUBULATION IN SAID PORTION OF REDUCED DIAMETER. 